Chemistry Fundamental Principles of Organic Chemistry BUMHS 2023
PMDC Verified Question 31 of 83
Number of primary carbon atoms present in isobutane is?
A
One
B
Two
C
Three
D
Four
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Three
Concept:

A primary (1°) carbon atom is defined as a carbon atom that is directly bonded to only one other carbon atom.

Solution:

  • The IUPAC name for isobutane is 2-methylpropane.


  • Its structure is \( \text{CH}_3\text{-CH(CH}_3\text{)-CH}_3 \).


  • The central carbon is bonded to three other carbons, making it a tertiary (3°) carbon.


  • The three methyl (\( \text{-CH}_3 \)) groups surrounding it are each bonded to only the central carbon. Therefore, all three of them are primary carbons.


Why other options are incorrect:

Counting the central carbon would be incorrect as it is tertiary. The molecule only has 4 carbons total, 3 of which are primary.

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